Several film materials are available which are water soluble and which can be formed into envelopes in which premeasured amounts of laundry additives can be sealed. Methyl cellulose, polyethylene oxide and polyvinyl alcohol are particularly useful film materials of this nature. Methyl cellulose films generally do not have sufficient solubility at higher water temperatures. Polyethylene oxide films tend to absorb moisture too readily and become tacky.
Polyvinyl alcohol films do not have the problems of methyl cellulose or polyethylene oxide films. However, when these films are placed in solutions containing borate at levels and pHs frequently encountered in laundry applications, the rate of solubility of such films is severely reduced. Yet, borate is often present in clothes washing liquors and the like, since one of the most widely used bleaching compositions is principally sodium perborate, which forms borate ions in solution. Other borate sources such as borax, are also often used as laundry additives.